In one method of manufacturing electrical terminals, the terminals are stamped and formed from a metal strip and are attached to a carrier strip. This carrier strip is useful for strip feeding the terminals through successive manufacturing operations. One necessary manufacturing operation involves plating, i.e., electroplating the electrical contact surfaces of the noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating, will enhance conductivity of the terminals. The high cost of these metals has necessitated precision deposition on the contact surfaces of the terminals, and not on surfaces of the terminals on which plating is unnecessary.
Apparatus for plating is called a plating cell and includes an electrical anode, an electrical cathode comprised of the strip fed terminals, and a plating solution, i.e., an electrolyte of metal ions. A strip feeding means feeds the strip to a strip guide. The strip guide guides the terminals through a plating zone while the terminals are being plated. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode through the plating solution to the terminals. The metal ions deposit as metal plating on those terminals surfaces in contact with the plating solution.
One method to achieve selective plating is to mask those areas of a workpiece that are not to be plated with a plating resist. Typically the resist is removed from the workpiece after plating. Another method is to use an apparatus having belts against which the workpiece lies, such that the belts mask the areas to remain unplated. This type of apparatus also requires means for driving the belt or belts along a continuous path through the apparatus in addition to means for moving the workpiece through the apparatus against the belts.
Other means for selectively plating components such as dip plating or tip plating involve passing one end or the other of the contact through the plating solution. These methods are unsatisfactory when the plating zone lies at center of a strip of electrical contacts.
U.S. Pat. Nos. 4,564,430; 4,597,564; and 4,597,845 disclose a continuous contact plating apparatus and method therefore, wherein the apparatus uses a continuously moving brush belt containing plating solution brought into contact against a webbed workpiece which plates selective portions of the continuous webbed workpiece. The belt is continuously replenished with plating solution through a box manifold. The belt is made of open-cell foam or absorbent material which wicks the plating solution and brushes it on the desired area of the cathodically charged web workpiece. The workpiece and brush belt are brought into precise contact at openings in a header of the box manifold where plating takes place.
These patents also teach a guide for the webbed workpiece that is adjustable along more than one axis for contacting the brush belt with the webbed workpiece with a range of contact pressure and angles. The brushed belt of this system is comprised of a continuous loop of material that is a carrier for a continuous loop of absorbent material that in fact is the brush. The carrier and the brush material must both be chemically inert to the plating solution used with the apparatus. Furthermore the brush must be periodically replaced as it wears out.
It is desirable, therefore, to have a selective plating apparatus for continuously plating a strip of electrical contacts or other workpiece that does not require belts, either to plate a selective area or to mask an area that is not to be plated on the workpiece.